The present invention relates to a cylinder throw apparatus for various types of printing presses such as an offset rotary press or intaglio printing press, which presses/separates a printing cylinder such as a blanket cylinder or impression cylinder against/from a corresponding cylinder, and at the same time, automatically controls a gap between the printing cylinder and its corresponding cylinder in correspondence with a paper thickness.
As shown in FIGS. 5 and 6, for example, an offset rotary press comprises a plate cylinder 1, a blanket cylinder 2, and an impression cylinder 3. A printing plate is mounted on the circumferential surface of the plate cylinder 1. The blanket cylinder 2 having a blanket mounted on its circumferential surface is in contact with the plate cylinder 1 during the printing operation. The impression cylinder 3 is in contact with the blanket cylinder 2 during the printing operation. Of these printing cylinders 1, 2, and 3, the plate cylinder 1 and the impression cylinder 3 have shafts rotatably supported, through bearings (none are shown), on left and right frames 5 provided to a printing unit 4, respectively. A shaft 6 of the blanket cylinder 2 is rotatably supported by eccentric bearings 7 (to be described later in detail) fitted in the left and right frames 5. More specifically, the positions of the shafts of the plate cylinder 1 and the impression cylinder 3 are fixed with respect to the left and right frames 5. On the other hand, the position of the shaft 6 of the blanket cylinder 2 is movable with respect to the left and right frames 5.
A swing lever 9 and an L-shaped cam lever 10 are integrally pivotally supported by a stud 8 projecting outward from one of the frames 5 near the end shaft of the impression cylinder 3. A lever shaft 11 having two ends axially supported on the left and right frames 5 is located above the stud 8. A coupling lever 13 coupled to the swinging end of the swing lever 9 by a bar 12 is axially mounted on one projecting portion of the lever shaft 11.
Another coupling lever 14 is axially mounted on the other projecting portion of the lever shaft 11. Cam followers 15 and 16 are pivotally mounted on the fork-like swinging end portions of the cam lever 10, respectively. The cam followers 15 and 16 are respectively in contact with the outer circumferential cam surfaces of two cams 17 and 18, both of which are supported on one of the frames to be rotated.
The above-described eccentric bearings 7 comprise outer eccentric bearings 71 and inner eccentric bearings 72, respectively. The outer eccentric bearings 71 comprise housings 19 pivotally fitted in bearing holes 5a in the frames 5, and inner rings 22 rotatably fitted, through needle rollers 21, in outer rings 20 fitted and held on the housings 19. The inner eccentric bearings 72 use the inner rings 22 as outer rings (to be referred to as outer rings 22 hereinafter) and comprise the outer rings 22 and inner rings 24 rotatably fitted in the outer rings 22 through conical rollers 23, respectively.
The distal end portions of handles 25 supported on the frames 5 are pivotally mounted on the housings 19, respectively. When the handles 25 are manually rotated to be moved, the outer eccentric bearings 71 are pivoted. One of bearing levers 26 fixed on the outer rings 22 of the inner eccentric bearings 72 is coupled to the coupling lever 13 by a rod 27. When the cam 17 is rotated, the inner eccentric bearings 72 are pivoted through the cam lever 10 or the like.
FIG. 7 shows movements of the axes of the blanket cylinder 2 and the eccentric bearings 7 when the eccentric bearings 7 are pivoted. This operation will be described with reference to FIGS. 5 and 6. Referring to FIG. 7, the axis of the blanket cylinder 2 when the blanket cylinder 2 is in contact with the plate cylinder 1 and the impression cylinder 3, i.e., in a so-called impression-on state is indicated by reference symbol B.
When the blanket cylinder 2 is to be separated from the plate cylinder 1 and the impression cylinder 3 to obtain a so-called impression throw-off state upon ending of the printing operation, the cams 17 and 18 are pivoted so that the inner eccentric bearings 72 slide along the outer rings 22 to be pivoted. In this case, the axis of the blanket cylinder 2 is moved on the arc centered on the axis M from the position indicated by reference symbol B to the position indicated by reference symbol B.sub.2 in FIG. 7 since the axis of the outer rings 22, indicated by reference symbol M, and the axis B of the blanket cylinder 2 are offset from each other. As a result, a gap indicated by reference symbol S.sub.1 in FIG. 7 is formed between the blanket cylinder 2 and the plate cylinder 1 while a gap indicated by reference symbol S.sub.2 in FIG. 7 is formed between the blanket cylinder 2 and the impression cylinder 3.
If thin paper 26 is replaced with thick paper having a thickness indicated by reference symbol T in FIG. 7, the operator grips and operates the handles 25 to pivot the outer eccentric bearings 71. In this case, the axis M of the outer rings 22 of the inner eccentric bearings 72 is moved on the arc centered on the axis F from the position indicated by reference symbol M to the position indicated by reference symbol M.sub.2 because the axis of the housings 19, indicated by reference symbol F, and the axis M of the outer rings 22 of the inner eccentric bearings 72 are offset from each other. As a result, a gap indicated by reference symbol T.sub.1 in FIG. 7 is formed between the blanket cylinder 2 and the impression cylinder 3, thereby obtaining a proper printing pressure for the thick paper.
In the conventional cylinder throw apparatus as described above, however, the cams 17 and 18 and many levers for transmitting the rotation of the both cams to the eccentric bearings 7 are required. In addition, since the eccentric bearings 7 comprise the outer eccentric bearings 71 and the inner eccentric bearings 72, the structure is complicated to cause an increase in number of components. It is also difficult to automatize the whole apparatus so that the operator load is increased. Furthermore, because the paper thickness adjustment operation is separately required, the preparation time cannot be shortened, thereby degrading the operating ratio of the printing press.
A cylinder throw apparatus in which eccentric bearings are pivoted by driving a motor to perform an impression-on/impression throw-off operation of a blanket cylinder axially supported by the eccentric bearings with respect to a plate cylinder and an impression cylinder is disclosed in Japanese Utility Model Laid-Open No. 56-26249. In this cylinder throw apparatus, however, a paper thickness adjusting mechanism for adjusting a gap between the blanket cylinder and the impression cylinder in correspondence with the paper thickness is not incorporated in the motor drive system. For this reason, the operator must manually pivot other eccentric bearings in correspondence with the paper thickness so that adjustment is cumbersome, and the structure is complicated. In addition, in the above cylinder throw apparatus, not the blanket cylinder but its corresponding cylinder, i.e., the impression cylinder is moved for paper thickness adjustment. No problem is posed in use of a web rotary press. However, in a sheet-fed press, when the impression cylinder corresponding to the blanket cylinder is moved for paper thickness adjustment, the relative positions of the grippers of the impression cylinder and the grippers of a transfer cylinder in contact with the impression cylinder are changed. Therefore, transfer of the paper between the transfer and impression cylinders becomes unstable.